Our Program on the Structural Biology of HIV Assembly, Budding, and Entry will focus on understanding and inhibiting the molecular interactions that allow HIV to assemble and bud from one cell and subsequently re- enter a new cell, thereby spreading infection. The Program is organized into five independent, but complementary, projects: 1) Structural Biology of HIV Budding (C.P. Hill, PI). This project will employ high throughput ?proteomics? and crystallographic approaches to define and determine the structures of cellular proteins and complexes involved in HIV-1 budding, including TsglO1 and proteins in the vacuolar protein sorting pathway. 2) Cryoelectron Tomography of HIV (G.J. Jensen, PI). Cryoelectron tomographic reconstructions of HIV virus-like particles will be determined at multiple stages of development, from initial budding to maturity. This work will capitalize on recent advances in electron microscopy to characterize the organization of HIV particles at near molecular resolution. 3) Inhibitors of HIV Assembly and Budding (W.I. Sundquist, PI). Structure-assisted development of inhibitors of HIV budding will be pursued using newly discovered inhibitors of the HIV-1 p6/Tsgl01 interaction and the three dimensional structure of this complex as a starting point. Inhibitors of HIV capsid assembly will also be pursued, starting with the development and implementation of high throughput screening protocols for discovering small molecule capsid assembly inhibitors. 4) Inhibition of HIV Entry and Envelope Folding (M.S. Kay, PI). This project will apply recent findings about the gp41- mediated viral fusion pathway to design and select inhibitors of viral entry and disrupt folding of the envelope protein. In summary, our Program will provide significant insights into how the HIV virion functions as a machine that can enter and exit cells, and how these processes can be inhibited.